With an explosive growth of smart phones and tablets, touch screens are widely applied in daily life, and more and more application software require touches with higher precision. Since a finger is too thick, with which it is hard to perform precise writing and quick writing on a small-sized screen, stylus pens for touch screens are used more and more widely, and the requirements for the performance of the stylus pens are higher and higher.
The stylus pens for touch screens mainly include passive pens and active pens. The passive pen functions as a finger of human being. When the passive pen touches a touch display screen, a small part of current on the touch display screen flows from a touch point to the passive pen, which equals to a change of an electrode capacitor at the touch point, by detecting the change of the electrode capacitor of a touch chip of the touch display screen, the position of the touch point can be determined. Normally, the passive pen cannot express the brush stroke and the pressure degree of the pen, so it cannot represent the line and the thickness and the aesthetic perception of a character. Meanwhile, the active pen is a stylus pen solution implemented based on the existing capacitive touch screen system hardware, with higher precision, low cost and good user experience, so that it is different from the passive pen. Active pen itself can function as a signal transmitting source, which can transmit an actuating signal, so as to change the electric field of a touch point and further to change the electrode capacitor at the touch point, and the touch chip of the touch screen may determine the position of the touch point by detecting the change of the electrode capacitor.
The active pen may implement a variation of a line width by pressure sensing principle, i.e., by adding a pressure sensor, which simulates real brush strokes and lines according to pressure signals, so that the pen can sense the variation of a user's handwriting force, so as to change the thickness of the brush stroke according to the variation of the handwriting force, to achieve a good user experience. However, such active pen has a higher requirement on the material of the pen tip, which costs higher; further, the pen tip of such active pen may cause physical damages on the touch screen, which may damage the structure of the surface layer of the touch screen.